A photographic material such as photographic film and photographic paper is generally produced by coating a photographic emulsion and other liquids on a wide plastic web (or a tape of pulp paper coated with resin) to form a photographic emulsion layer and other auxiliary layers. The web having the photosensitive layer is then wound up, and stored or transported in the form of a roll. On the occasion of practical use, the coated web is drew from the roll and cut to give a photosensitive film (e.g., photographic film or paper sheet) of a desired size.
In storage or transportation, the roll of photosensitive material is usually fastened with a fastening tape so as not to loosen. As the fastening tape, a thermal connective tape with hot-melt pressure sensitive adhesive composition is unfavorable because photographic material is sensitive to heat so that the applied heat often deteriorates the photographic material. In contrast, a pressure sensitive adhesive tape is easily attached onto the end and the surface of the roll using no heat, and is easily removed from them. Therefore, the pressure sensitive adhesive tape is practically used for packaging photographic materials.
In general, the pressure sensitive adhesive film comprises a support film and a pressure sensitive adhesive composition provided thereon. The adhesive composition contains a main pressure sensitive adhesive component of elastomer or acrylic resin and, if needed, other auxiliary components such as a vulcanization accelerator (e.g., a sulfur-containing compound such as disulfide) and rosin.
Besides as the fastening tape, the pressure sensitive adhesive film is often used for packaging photographic materials. For example, the pressure sensitive adhesive film is used in the form of a pressure sensitive adhesive label to be placed on each individual photographic film or paper, or to shield a light-shielding bag which contains a photographic film or paper. Further, the end of photographic film is fixed on a backing paper having the pressure sensitive adhesive sheet, and then wound up together with the backing paper to prepare a roll film (e.g., Brownie film). The pressure sensitive adhesive film is also used for connecting a black leader film to a photosensitive material to prepare a printing photosensitive roll for processing under daylight.
With respect to the pressure sensitive adhesive composition for the pressure sensitive adhesive film, various studies have been done. Since the pressure sensitive adhesive composition is employed in direct contact with photographic materials, it should not impair photographic characteristics of the photographic material. Further, the pressure sensitive adhesive composition is also required to give adequate adhesiveness and to be chemically stable. According to Japanese Patent Provisional Publication No. H3(1991)-177473, a pressure sensitive adhesive composition comprising acrylic polymer satisfies those conditions and hence is suitably employable for a pressure sensitive adhesive film for packaging photographic materials.
Although the acrylic pressure sensitive adhesive composition has good characteristics for packaging photographic material, however, the present inventors have found that further improvements are required in consideration of influences on photographic characteristics and adhesion given to photographic materials by the acrylic pressure sensitive adhesive composition.
Accordingly, it is an object of the present invention to provide an improved acrylic pressure sensitive adhesive composition or an improved elastomer pressure sensitive adhesive composition prepared by graft polymerization of an acrylic monomer.
Further, it is another object of the invention to provide a pressure sensitive adhesive film provided with the pressure sensitive adhesive composition.